#!/usr/bin/env python3
#
#  d3des.py - DES implementation
#
#  Copyright (c) 2009 by Yusuke Shinyama
#

# This is a Python rewrite of `d3des.c` by Richard Outerbridge.
#
# I referred to the original VNC viewer code for the changes that
# is necessary to maintain the exact behavior of the VNC protocol.
# Two constants and two functions were added to the original d3des
# code.  These added parts were written in Python and marked
# below.  I believe that the added parts do not make this program
# a "derivative work" of the VNC viewer (which is GPL'ed and
# written in C), but if there's any problem, let me know.
#
# Yusuke Shinyama (yusuke at cs dot nyu dot edu)


#  D3DES (V5.09) -
#
#  A portable, public domain, version of the Data Encryption Standard.
#
#  Written with Symantec's THINK (Lightspeed) C by Richard Outerbridge.
#  Thanks to: Dan Hoey for his excellent Initial and Inverse permutation
#  code;  Jim Gillogly & Phil Karn for the DES key schedule code; Dennis
#  Ferguson, Eric Young and Dana How for comparing notes; and Ray Lau,
#  for humouring me on.
#
#  Copyright (c) 1988 by Richard Outerbridge.
#  (GEnie : OUTER; CIS : [71755,204]) Graven Imagery, 1992.
#

from struct import pack, unpack

###################################################
#
# start: changes made for VNC.
#

# This constant was taken from vncviewer/rfb/vncauth.c:
vnckey = [23, 82, 107, 6, 35, 78, 88, 7]

# This is a departure from the original code.
# bytebit = [ 0o200, 0o100, 0o40, 0o20, 0o10, 0o4, 0o2, 0o1 ] # original
bytebit = [0o1, 0o2, 0o4, 0o10, 0o20, 0o40, 0o100, 0o200]  # VNC version


# two password functions for VNC protocol.


def decrypt_passwd(data):
    dk = deskey(pack('8B', *vnckey), True)
    return desfunc(data, dk)


def generate_response(passwd, challenge):
    ek = deskey((passwd + b'\x00' * 8)[:8], False)
    return desfunc(challenge[:8], ek) + desfunc(challenge[8:], ek)


#
# end: changes made for VNC.
#
###################################################


bigbyte = [
    0x800000, 0x400000, 0x200000, 0x100000,
    0x80000, 0x40000, 0x20000, 0x10000,
    0x8000, 0x4000, 0x2000, 0x1000,
    0x800, 0x400, 0x200, 0x100,
    0x80, 0x40, 0x20, 0x10,
    0x8, 0x4, 0x2, 0x1,
]

# Use the key schedule specified in the Standard (ANSI X3.92-1981).

pc1 = [
    56, 48, 40, 32, 24, 16, 8, 0, 57, 49, 41, 33, 25, 17,
    9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51, 43, 35,
    62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21,
    13, 5, 60, 52, 44, 36, 28, 20, 12, 4, 27, 19, 11, 3
]

totrot = [1, 2, 4, 6, 8, 10, 12, 14, 15, 17, 19, 21, 23, 25, 27, 28]

pc2 = [
    13, 16, 10, 23, 0, 4, 2, 27, 14, 5, 20, 9,
    22, 18, 11, 3, 25, 7, 15, 6, 26, 19, 12, 1,
    40, 51, 30, 36, 46, 54, 29, 39, 50, 44, 32, 47,
    43, 48, 38, 55, 33, 52, 45, 41, 49, 35, 28, 31
]


def deskey(key, decrypt):  # Thanks to James Gillogly & Phil Karn!
    key = unpack('8B', key)

    pc1m = [0] * 56
    pcr = [0] * 56
    kn = [0] * 32

    for j in range(56):
        l = pc1[j]
        m = l & 0o7
        if key[l >> 3] & bytebit[m]:
            pc1m[j] = 1
        else:
            pc1m[j] = 0

    for i in range(16):
        if decrypt:
            m = (15 - i) << 1
        else:
            m = i << 1
        n = m + 1
        kn[m] = kn[n] = 0
        for j in range(28):
            l = j + totrot[i]
            if l < 28:
                pcr[j] = pc1m[l]
            else:
                pcr[j] = pc1m[l - 28]
        for j in range(28, 56):
            l = j + totrot[i]
            if l < 56:
                pcr[j] = pc1m[l]
            else:
                pcr[j] = pc1m[l - 28]
        for j in range(24):
            if pcr[pc2[j]]:
                kn[m] |= bigbyte[j]
            if pcr[pc2[j + 24]]:
                kn[n] |= bigbyte[j]

    return cookey(kn)


def cookey(raw):
    key = []
    for i in range(0, 32, 2):
        (raw0, raw1) = (raw[i], raw[i + 1])
        k = (raw0 & 0x00fc0000) << 6
        k |= (raw0 & 0x00000fc0) << 10
        k |= (raw1 & 0x00fc0000) >> 10
        k |= (raw1 & 0x00000fc0) >> 6
        key.append(k)
        k = (raw0 & 0x0003f000) << 12
        k |= (raw0 & 0x0000003f) << 16
        k |= (raw1 & 0x0003f000) >> 4
        k |= (raw1 & 0x0000003f)
        key.append(k)
    return key


SP1 = [
    0x01010400, 0x00000000, 0x00010000, 0x01010404,
    0x01010004, 0x00010404, 0x00000004, 0x00010000,
    0x00000400, 0x01010400, 0x01010404, 0x00000400,
    0x01000404, 0x01010004, 0x01000000, 0x00000004,
    0x00000404, 0x01000400, 0x01000400, 0x00010400,
    0x00010400, 0x01010000, 0x01010000, 0x01000404,
    0x00010004, 0x01000004, 0x01000004, 0x00010004,
    0x00000000, 0x00000404, 0x00010404, 0x01000000,
    0x00010000, 0x01010404, 0x00000004, 0x01010000,
    0x01010400, 0x01000000, 0x01000000, 0x00000400,
    0x01010004, 0x00010000, 0x00010400, 0x01000004,
    0x00000400, 0x00000004, 0x01000404, 0x00010404,
    0x01010404, 0x00010004, 0x01010000, 0x01000404,
    0x01000004, 0x00000404, 0x00010404, 0x01010400,
    0x00000404, 0x01000400, 0x01000400, 0x00000000,
    0x00010004, 0x00010400, 0x00000000, 0x01010004,
]

SP2 = [
    0x80108020, 0x80008000, 0x00008000, 0x00108020,
    0x00100000, 0x00000020, 0x80100020, 0x80008020,
    0x80000020, 0x80108020, 0x80108000, 0x80000000,
    0x80008000, 0x00100000, 0x00000020, 0x80100020,
    0x00108000, 0x00100020, 0x80008020, 0x00000000,
    0x80000000, 0x00008000, 0x00108020, 0x80100000,
    0x00100020, 0x80000020, 0x00000000, 0x00108000,
    0x00008020, 0x80108000, 0x80100000, 0x00008020,
    0x00000000, 0x00108020, 0x80100020, 0x00100000,
    0x80008020, 0x80100000, 0x80108000, 0x00008000,
    0x80100000, 0x80008000, 0x00000020, 0x80108020,
    0x00108020, 0x00000020, 0x00008000, 0x80000000,
    0x00008020, 0x80108000, 0x00100000, 0x80000020,
    0x00100020, 0x80008020, 0x80000020, 0x00100020,
    0x00108000, 0x00000000, 0x80008000, 0x00008020,
    0x80000000, 0x80100020, 0x80108020, 0x00108000,
]

SP3 = [
    0x00000208, 0x08020200, 0x00000000, 0x08020008,
    0x08000200, 0x00000000, 0x00020208, 0x08000200,
    0x00020008, 0x08000008, 0x08000008, 0x00020000,
    0x08020208, 0x00020008, 0x08020000, 0x00000208,
    0x08000000, 0x00000008, 0x08020200, 0x00000200,
    0x00020200, 0x08020000, 0x08020008, 0x00020208,
    0x08000208, 0x00020200, 0x00020000, 0x08000208,
    0x00000008, 0x08020208, 0x00000200, 0x08000000,
    0x08020200, 0x08000000, 0x00020008, 0x00000208,
    0x00020000, 0x08020200, 0x08000200, 0x00000000,
    0x00000200, 0x00020008, 0x08020208, 0x08000200,
    0x08000008, 0x00000200, 0x00000000, 0x08020008,
    0x08000208, 0x00020000, 0x08000000, 0x08020208,
    0x00000008, 0x00020208, 0x00020200, 0x08000008,
    0x08020000, 0x08000208, 0x00000208, 0x08020000,
    0x00020208, 0x00000008, 0x08020008, 0x00020200,
]

SP4 = [
    0x00802001, 0x00002081, 0x00002081, 0x00000080,
    0x00802080, 0x00800081, 0x00800001, 0x00002001,
    0x00000000, 0x00802000, 0x00802000, 0x00802081,
    0x00000081, 0x00000000, 0x00800080, 0x00800001,
    0x00000001, 0x00002000, 0x00800000, 0x00802001,
    0x00000080, 0x00800000, 0x00002001, 0x00002080,
    0x00800081, 0x00000001, 0x00002080, 0x00800080,
    0x00002000, 0x00802080, 0x00802081, 0x00000081,
    0x00800080, 0x00800001, 0x00802000, 0x00802081,
    0x00000081, 0x00000000, 0x00000000, 0x00802000,
    0x00002080, 0x00800080, 0x00800081, 0x00000001,
    0x00802001, 0x00002081, 0x00002081, 0x00000080,
    0x00802081, 0x00000081, 0x00000001, 0x00002000,
    0x00800001, 0x00002001, 0x00802080, 0x00800081,
    0x00002001, 0x00002080, 0x00800000, 0x00802001,
    0x00000080, 0x00800000, 0x00002000, 0x00802080,
]

SP5 = [
    0x00000100, 0x02080100, 0x02080000, 0x42000100,
    0x00080000, 0x00000100, 0x40000000, 0x02080000,
    0x40080100, 0x00080000, 0x02000100, 0x40080100,
    0x42000100, 0x42080000, 0x00080100, 0x40000000,
    0x02000000, 0x40080000, 0x40080000, 0x00000000,
    0x40000100, 0x42080100, 0x42080100, 0x02000100,
    0x42080000, 0x40000100, 0x00000000, 0x42000000,
    0x02080100, 0x02000000, 0x42000000, 0x00080100,
    0x00080000, 0x42000100, 0x00000100, 0x02000000,
    0x40000000, 0x02080000, 0x42000100, 0x40080100,
    0x02000100, 0x40000000, 0x42080000, 0x02080100,
    0x40080100, 0x00000100, 0x02000000, 0x42080000,
    0x42080100, 0x00080100, 0x42000000, 0x42080100,
    0x02080000, 0x00000000, 0x40080000, 0x42000000,
    0x00080100, 0x02000100, 0x40000100, 0x00080000,
    0x00000000, 0x40080000, 0x02080100, 0x40000100,
]

SP6 = [
    0x20000010, 0x20400000, 0x00004000, 0x20404010,
    0x20400000, 0x00000010, 0x20404010, 0x00400000,
    0x20004000, 0x00404010, 0x00400000, 0x20000010,
    0x00400010, 0x20004000, 0x20000000, 0x00004010,
    0x00000000, 0x00400010, 0x20004010, 0x00004000,
    0x00404000, 0x20004010, 0x00000010, 0x20400010,
    0x20400010, 0x00000000, 0x00404010, 0x20404000,
    0x00004010, 0x00404000, 0x20404000, 0x20000000,
    0x20004000, 0x00000010, 0x20400010, 0x00404000,
    0x20404010, 0x00400000, 0x00004010, 0x20000010,
    0x00400000, 0x20004000, 0x20000000, 0x00004010,
    0x20000010, 0x20404010, 0x00404000, 0x20400000,
    0x00404010, 0x20404000, 0x00000000, 0x20400010,
    0x00000010, 0x00004000, 0x20400000, 0x00404010,
    0x00004000, 0x00400010, 0x20004010, 0x00000000,
    0x20404000, 0x20000000, 0x00400010, 0x20004010,
]

SP7 = [
    0x00200000, 0x04200002, 0x04000802, 0x00000000,
    0x00000800, 0x04000802, 0x00200802, 0x04200800,
    0x04200802, 0x00200000, 0x00000000, 0x04000002,
    0x00000002, 0x04000000, 0x04200002, 0x00000802,
    0x04000800, 0x00200802, 0x00200002, 0x04000800,
    0x04000002, 0x04200000, 0x04200800, 0x00200002,
    0x04200000, 0x00000800, 0x00000802, 0x04200802,
    0x00200800, 0x00000002, 0x04000000, 0x00200800,
    0x04000000, 0x00200800, 0x00200000, 0x04000802,
    0x04000802, 0x04200002, 0x04200002, 0x00000002,
    0x00200002, 0x04000000, 0x04000800, 0x00200000,
    0x04200800, 0x00000802, 0x00200802, 0x04200800,
    0x00000802, 0x04000002, 0x04200802, 0x04200000,
    0x00200800, 0x00000000, 0x00000002, 0x04200802,
    0x00000000, 0x00200802, 0x04200000, 0x00000800,
    0x04000002, 0x04000800, 0x00000800, 0x00200002,
]

SP8 = [
    0x10001040, 0x00001000, 0x00040000, 0x10041040,
    0x10000000, 0x10001040, 0x00000040, 0x10000000,
    0x00040040, 0x10040000, 0x10041040, 0x00041000,
    0x10041000, 0x00041040, 0x00001000, 0x00000040,
    0x10040000, 0x10000040, 0x10001000, 0x00001040,
    0x00041000, 0x00040040, 0x10040040, 0x10041000,
    0x00001040, 0x00000000, 0x00000000, 0x10040040,
    0x10000040, 0x10001000, 0x00041040, 0x00040000,
    0x00041040, 0x00040000, 0x10041000, 0x00001000,
    0x00000040, 0x10040040, 0x00001000, 0x00041040,
    0x10001000, 0x00000040, 0x10000040, 0x10040000,
    0x10040040, 0x10000000, 0x00040000, 0x10001040,
    0x00000000, 0x10041040, 0x00040040, 0x10000040,
    0x10040000, 0x10001000, 0x10001040, 0x00000000,
    0x10041040, 0x00041000, 0x00041000, 0x00001040,
    0x00001040, 0x00040040, 0x10000000, 0x10041000,
]


def desfunc(block, keys):
    (leftt, right) = unpack('>II', block)

    work = ((leftt >> 4) ^ right) & 0x0f0f0f0f
    right ^= work
    leftt ^= (work << 4)
    work = ((leftt >> 16) ^ right) & 0x0000ffff
    right ^= work
    leftt ^= (work << 16)
    work = ((right >> 2) ^ leftt) & 0x33333333
    leftt ^= work
    right ^= (work << 2)
    work = ((right >> 8) ^ leftt) & 0x00ff00ff
    leftt ^= work
    right ^= (work << 8)
    right = ((right << 1) | ((right >> 31) & 1)) & 0xffffffff
    work = (leftt ^ right) & 0xaaaaaaaa
    leftt ^= work
    right ^= work
    leftt = ((leftt << 1) | ((leftt >> 31) & 1)) & 0xffffffff

    for i in range(0, 32, 4):
        work = (right << 28) | (right >> 4)
        work ^= keys[i]
        fval = SP7[work & 0x3f]
        fval |= SP5[(work >> 8) & 0x3f]
        fval |= SP3[(work >> 16) & 0x3f]
        fval |= SP1[(work >> 24) & 0x3f]
        work = right ^ keys[i + 1]
        fval |= SP8[work & 0x3f]
        fval |= SP6[(work >> 8) & 0x3f]
        fval |= SP4[(work >> 16) & 0x3f]
        fval |= SP2[(work >> 24) & 0x3f]
        leftt ^= fval
        work = (leftt << 28) | (leftt >> 4)
        work ^= keys[i + 2]
        fval = SP7[work & 0x3f]
        fval |= SP5[(work >> 8) & 0x3f]
        fval |= SP3[(work >> 16) & 0x3f]
        fval |= SP1[(work >> 24) & 0x3f]
        work = leftt ^ keys[i + 3]
        fval |= SP8[work & 0x3f]
        fval |= SP6[(work >> 8) & 0x3f]
        fval |= SP4[(work >> 16) & 0x3f]
        fval |= SP2[(work >> 24) & 0x3f]
        right ^= fval

    right = (right << 31) | (right >> 1)
    work = (leftt ^ right) & 0xaaaaaaaa
    leftt ^= work
    right ^= work
    leftt = (leftt << 31) | (leftt >> 1)
    work = ((leftt >> 8) ^ right) & 0x00ff00ff
    right ^= work
    leftt ^= (work << 8)
    work = ((leftt >> 2) ^ right) & 0x33333333
    right ^= work
    leftt ^= (work << 2)
    work = ((right >> 16) ^ leftt) & 0x0000ffff
    leftt ^= work
    right ^= (work << 16)
    work = ((right >> 4) ^ leftt) & 0x0f0f0f0f
    leftt ^= work
    right ^= (work << 4)

    leftt &= 0xffffffff
    right &= 0xffffffff
    return pack('>II', right, leftt)
